a major crack discovered at the Penly power plant, in Seine-Maritime

The major crack discovered by EDF on one of its nuclear reactors at the Penly power plant (Seine-Maritime), is a “serious subject” and “poses a problem”, underlined Wednesday before the senators the president of the Nuclear Safety Authority (ASN). “There has been a new element in recent weeks which is the discovery of stress corrosion cracking on one of the circuits of the Penly 1 reactor, which is very large since it is 23 mm for a total thickness of 27,” Bernard Doroszczuk said of the anomaly reported on Tuesday.

“These are not micro-cracks”

These are cracks in emergency pipes to allow water to flood a reactor in the event of a nuclear accident. These pipes are not used in the normal operation of a plant. “Stress corrosion is a serious subject. These are not micro-cracks. When there is only 4 mm left over a thickness of 27, that is a problem”, he added, on the occasion of a senatorial hearing on a government plan to reform nuclear safety.

A crack discovered in 2021 but more important today

This subject of corrosion, a source of micro-cracks, was discovered at the end of 2021, in connection with the particular geometry of the pipes of the most recent reactors, and had prompted EDF to shut down part of its fleet for inspection and repair. But this time, the crack is more important, and linked to another factor dating from the construction of the plant, in the 1990s. The ASN therefore summoned EDF on Tuesday to “revise its strategy” for dealing with the problem. “The phenomenon there (in Penly, editor’s note) is different: it is a weld that has been repaired twice because the alignment of the pipes before the weld was forced”, continued the boss of the ASN. “There was an approach which is not acceptable, which consisted of forcing the pipes a little to align them to weld them, and there were defects on this weld which led to a second repair”.

So “we are on a singular point, we are not on a generic explanation. This does not mean that this fault cannot appear elsewhere, so we asked EDF to quickly identify similar cases that may exist on the other reactors to be able to go and check these welds, and we put pressure on EDF to define an evolution of its control strategy”, he said again.